The advent of two-way paging raises many system issues as well as issues that would require greater efficiency at a portable subscriber unit. With the addition of a transmitter to a traditional one-way paging subscriber unit, battery life becomes more significant than usual. On a system level, a transmitter at the portable subscriber unit provides many benefits that can still use further refinements. For example, a system that does not adjust their transmission power, either from an outbound paging transmitter to a portable subscriber unit or from the portable subscriber unit inbound to the system reduces the overall system efficiency as well as battery life at the subscriber unit. When transmitters needlessly transmit at full power, system capacity is jeopardize and the risk of on-channel intermodulation is increased. There are existing methods that use Received Signal Strength Indicator (RSSI) measurements, Signal Quality Evaluation (SQE) measurements, and/or color codes to adjust transmission power or to make transmission site selection decisions. These methods are adequate in many instances, but they are not accurate. For instance, these methods do not account for the terrain nor do they allow for automatic "boundary" site switching. Geographic information at a portable subscriber unit would thus be helpful in controlling many operations. Thus, a need exists incorporating geographic information for optimizing power transmission levels from either a portable subscriber unit's transmitter or an outbound transmitter. Additionally, geographic information would provide other benefits that would improve site selection decisions, battery life and synchronization among other benefits.